The Grapevine section of Interstate 5, the key artery linking southern and northern California, was shut down Thursday night. The area was blanketed with heavy snowfall that showed no immediate signs of stopping, leaving truckers and would-be travelers stranded.

The area was blanketed with heavy snowfall that showed no immediate signs of stopping, leaving truckers and would-be travelers stranded.

Police said the closure would remain in effect overnight and the roadway would be re-evaluated in the morning.

The day saw several accidents and spinouts on the mountain pass that led to a pair of closures, the second of which continued into the night.

Elsewhere, strawberry growers covered their crops while San Diego zookeepers turned on heaters for the chimpanzees.

Forecasters warned that a low pressure trough sinking over San Diego County and parts of neighboring Orange County could keep nightly temperatures below the freezing point in coastal areas, the low deserts and inland valleys, threatening orange, avocado orchards and other sensitive plants. The coldest nights were expected to hit Friday and Saturday.

Farmers were prepared to pull out giant fans to circulate the air and keep it from settling on their citrus trees, said Eric Larson of the San Diego County Farm Bureau. Other growers were placing soft cloth over their strawberries and flowers. The National Weather Service predicted overnight lows in the 20s in the lower deserts and key citrus-growing regions in the Central Valley, and in the 30s along the coast.

"These guys are going to be up all night watching thermometers," Larson said.

Freezing temperatures weren't the only weather challenge in Southern California, a region boasting one of the planet's most temperate climates.

Forecasters say a combination of high tides, high surf and strong winds will bring minor flooding to low-lying areas of the Southern California coast. The weather service issued coastal flood advisories for all counties from San Luis Obispo south to San Diego through Saturday morning.

Winds could gust to 60 mph there and up to 45 mph in valleys and coastal areas. Highs will only hit the 50s and 60s and rain showers are expected throughout the region.

Families pushed aside boogie boards and pulled out sleds as snow fell Thursday in the mountains of San Bernardino and Riverside counties. Chains were required on all vehicles.

Farther north in Sonoma County, homeless shelters started handing out extra warm clothes to protect the least fortunate from below-freezing overnight temperatures.

Workers at SeaWorld in San Diego planned to crank up the heat for their macaws, toucans and parrots. San Diego zookeepers were also heating rooms for chimpanzees, apes and other tropical animals.

"They'll probably be huddling together and not be in areas where people will be able to see them," said zoo spokeswoman Christina Simmons.